Causes of calcification Malignant tumors of the thyroid gland cause calcification due to rapid growth of cancer cells and proliferation of blood vessels and fibrous tissues in the tumor, which can easily lead to calcium salt deposition. In addition, calcification can also be caused by the secretion of substances such as glycoproteins and mucopolysaccharides by the tumor itself. Calcification can occur in malignant nodules as well as benign nodules, but the chance of calcification in malignant nodules is higher, ranging from 26% to 54% in the former and 8% to 32% in the latter. Calcification typing by ultrasound ① Microcalcifications: multiple strong echogenic dots (less than 2 m m ), clustered or scattered, with or without acoustic shadowing. When both microcalcifications and coarse calcifications are present in the nodule, the nodule is classified as a microcalcification type. (ii) Coarse calcification: a strong echogenic spot larger than 2 mm inside the nodule with acoustic shadow. (iii) Peripheral calcification: coarse calcification surrounding the nodule in a circular or curved shape. ④ Isolated calcified spots: are single coarse calcifications with no surrounding thyroid nodules. The relationship between calcifications and benign and malignant nodules Microcalcifications are often considered the most reliable indicator for the diagnosis of thyroid cancer and basically reflect the “sand bodies” in the pathology. Sandy bodies are characteristic of papillary thyroid carcinoma and can also be seen in follicular thyroid carcinoma, nodular goiter, follicular adenoma, and chronic lymphocytic thyroiditis. The specificity, positive predictive value and sensitivity of ultrasound showing microcalcifications for thyroid cancer diagnosis are 85%-94%, 69%-71% and 36%-59%, respectively. Peripheral calcification, coarse calcification, and isolated calcification are usually considered as indicators for the diagnosis of benign thyroid tumors, which are usually seen in benign diseases such as thyroid adenoma and nodular goiter, but all three of them can also occur in malignant nodules. In conclusion, calcification on ultrasound is a specific indicator for the diagnosis of thyroid cancer, and each type of calcification has a risk of malignancy from the point of view of screening for thyroid cancer.